The present invention relates to ink jet printers, and, in particular, to an improved ink jet printer constructed to more accurately and reliably discharge paper including discharging the paper without causing ink to smear on the discharged sheets of paper.
Reference is first made to FIGS. 32-34 which depict a conventional printer described in U.S. Pat. No. 5,299,875. This printer includes a printer body, generally indicated at 401. A paper feed tray 402 for receiving and setting a paper P which is delivered for printing, is positioned at a rear portion of body 401. A pair of support portions 403 and 404 and an edge separator 405 are positioned at a front portion of body 401. A pair of recesses 406 and 407 are provided in body 401 to receive support portion 403 and 404, respectively, during non-use and storage of the printer. An ink jet head (not shown) is positioned within body 401. Paper P is supplied to body 401 from paper feed tray 402. As shown in FIG. 34, after paper P is printed upon by the ink jet head, the paper is discharged while the side edges of paper P are guided and supported by support portions 403 and 404 and the central portion of paper P is guided and supported by edge separator 405. Supporting portion 404 is constructed to be slidable in the paperwidth direction (arrow b, FIG. 33) so as to be adjustable to correspond to the width of the paper P being printed upon. Furthermore, during storage of the printer when not in use, supporting portion 404 is constructed to face recess 406 and capable of rotation in the direction of arrow a (to the right of the paperwidth direction). Likewise, supporting portion 403 is constructed to face recess 407 and is capable of rotation.
In another type of conventional printer (not shown), an edge guide assembly may be provided to guide the edges of a paper set in a paper feed apparatus. The edge guides, which must be manually positioned, may be permitted to slide in the paper widthwise direction upon a shaft, for example, in order to be set to correspond to the width of a paper being fed into the printer.
Reference is now made to FIG. 35 which depicts a conventional ink jet printer, generally indicated as 500, described in Japanese Unexamined Patent Publication 341848/1992. Printer 500 includes a printing section, generally indicated at 501, which itself includes an ink jet head 502 and a paper guide member 506 spaced apart from ink jet head 502. Paper guide member 506 has a guide surface 506a which contacts the bottom surface of paper P and guides paper P through printing section 501. Printer 500 also includes paper feed rollers 504a, 504b which rotate as indicated by arrows z1, z2 respectively in FIG. 35, thereby feeding a sheet of paper P therebetween to printing section 501. Ink jet head 502 (hereinafter "head 502") discharges ink while moving reciprocally in a direction perpendicular to the paper surface of FIG. 35 and prints on the surface of paper P fed as it is fed to printing section 501 by paper feed rollers 504a, 504b. The width A represents the printing region within which head 502 prints on printer P. A pair of paper discharge rollers 505a and 505b are rotatably mounted in printer 500 and guide paper P out of printing section 501 so as to be discharged.
One common problem with the conventional ink jet printers described above which generally print by discharging ink on a paper and which further require continuous sheets to be continuously printed upon and discharged through the printing section is that there is insufficient time to permit the ink to dry on a previous sheet of paper before the next sheet of paper is discharged thereupon. Without any means to sufficiently separate each successive sheet of paper before the previous page dries, the next paper is discharged and slidably contacts the printed surface of the previous printed paper. Therefore, there is a high likelihood that the ink on the printed surface of the previous printed paper will smear.
One ink jet printer construction that has attempted to solve this problem is described in Japanese Unexamined Patent Publication 91861/1994, a perspective view of a paper discharge portion, generally indicated at 690, of the ink jet printer being depicted in FIGS. 36-39. Discharge portion 690 includes a frame 670 which includes thereon a pair of integrally formed supporting portions 691a and 691b which respectively guide and support from below each side portion of a paper P which has been previously printed upon (on an upper surface thereof) by means of a printing head (not shown) and is being discharged therefrom. Supporting portions 691a and 691b may be thin, integrally formed and not movable rib-like members, having their respective upper surfaces 691a', 691b' inclined upwards in the paper discharging direction. A transport section 680 includes a plurality of discharging rollers 682 for discharging paper P and eventually will be discharged onto a discharge plate 660 which may be rotatably mounted with respect to discharge frame 670.
An arm, generally indicated at 693, is rotatably mounted on a frame (not shown). Arm 693 includes a pushing-down portion 692, rotatably supported thereon and constructed of a notched roller (thin plate shaped star wheel). Pushing down portion 692 pushes down on the central portion of the paper P being discharged from discharged section 690.
The paper discharge operation of this conventional type of printer will now be described. Paper P is printed upon in the print section (not shown) and passes into discharge portion 690. At this time each side of paper P is guided upwardly by upper surfaces 691a', 691b' of respective supporting portions 691a and 691b. At the same time, although the central portion of paper P attempts to push pushing-down portion 692 upwardly while also rotating arm 693 upwardly, the central portion of the paper will gradually fall below pushing-down portion 692 and is urged downwardly due to the weight of pushing-down portion 692 and arm 693 against the central portion of paper P. Thus, as paper P is discharged it is forcibly urged into a concave shape as viewed in the discharging direction. This type of concave shape may also be achieved without a pushing down portion since the weight of the paper itself may cause the concavity thereof. Nonetheless, as paper P is forcibly urged into this concave shape, the paper will stiffen and will move along in the discharging direction as if it were floating. Because of this, as more particularly depicted in FIG. 37, the time until discharged paper P slidably contacts a printed surface P1f of paper P1 (previously printed, discharged, and stacked on a paper discharge tray 660) will be delayed. This method of delaying the subsequent sheet of paper from contacting the previously discharged sheet allows sufficient time for the ink to dry on printed paper P1 before contact with paper P takes place.
FIG. 38 illustrates paper P after being further discharged from discharge portion 690, and having its trailing edge Pb pass transport section 680. At this time, and without discharge rollers 682 acting on paper P, paper P loses its transporting force in the discharge direction. However, the rear portion Pc of paper P is maintained in its concave state by the remaining force of pushing-down portion 692 upon the central portion of rear portion Pc of paper P and the remaining action of support portions 691a, 691b upon the sides of paper P.
As shown in FIG. 39, when a subsequent sheet of paper P2 enters transport section 680, its leading edge P2a will then pass transport section 680. When leading edge P2a, contacts trailing edge Pb of the preceding paper P, discharge portion 690 and does not press against preceding paper P. The force applied by discharge portion 690 against preceding paper P ceases by the time it contacts subsequent paper P2. Preceding paper P is stacked on the earlier printed paper P1 (FIG. 37), and therefore the time until paper P2 contacts printed paper P1 is further delayed.
Referring once again to the ink jet printer depicted in FIGS. 32-34, when setting paper of different sizes in paper feed tray 402, it is necessary for the user to slide supporting portion 404 in the direction of arrow b (FIG. 33) to match the width of the paper set therein. However, supporting portion 404 is constructed to rotate only in the paperwidth direction (the sliding direction). Therefore, in the case of carelessness by the user, for example, support portion 404 may be slid by the user without first observing for the presence of obstructions in the sliding direction. In this way, force applied to support portion 404 in a direction in which there is no rotatability, because of an obstruction, for example, will cause damage to the printer and/or supporting portion. For example, if the previously described edge separator 405 is replaced with the aforementioned pushing-down portion, this pushing-down portion may become the above-mentioned obstruction, and there is an increased possibility that the construction of a printer that utilizes both the support portions 403, 404 and which attempts to reduce ink smearing by incorporating a pushing-down portion 692, will result in damage to the support portion 404 by the possible carelessness of the user when rotating support portions 403, 404.
Moreover, in printers having an edge guide it is necessary for the user to slide the edge guide to match the width of the paper when setting paper of a different size in the paper feeder. Accordingly, if it was desired to use both an edge guide and support portions, when setting paper of a different size in a paper feeder apparatus, the user must not only separately slide the edge guide, but also must slide a support portion to match the width of the paper. This multi-setting requirement is complicated and undesirable.
In particular, in the case where a paper feeder apparatus in which paper is set and a discharge portion in which paper is discharged are spaced apart and provided in different planes with respect to each other, and therefore a guide which may be set to guide the paper in the paper tray and a discharge portion are positioned far apart from each other, when setting paper of different sizes in the paper feeder apparatus, even if the user does not forget to slide the edge guide to match the width of the paper, the user may carelessly forget to slide the support portion in the discharge section. If the support portion is not slid to the proper position, a correct discharge operation will not be achieved and ink will smear on the previously discharged paper.
Still further, in an ink jet printer of the type depicted in FIG. 35, if paper P is warped into a concave shape, the leading edge of paper P might enter the space S between head 502 and discharge rollers 505a, 505b. If the leading edge of the warped sheet of paper enters space S, the section of the paper having already been printed upon may contact head 502, thereby smudging the not yet dried ink. Moreover, if the leading edge of the warped paper cannot be properly guided towards discharge rollers 505a, 505b, the leading edge of paper P will become jammed in space S thereby causing a paper jam condition.
Still further, in an ink jet printer having a paper discharge configuration of the type depicted in FIGS. 36-40 which is capable of printing on paper of different sizes and where paper of different sizes can be discharged, it is desirable that at least one supporting portion, 691a or 691b be capable of sliding so as to be adjustable to match the width of paper P delivered for printing. However, the sliding of the supporting portion requires a complicated and undesirable printer construction and operation.
On the other hand, as previously described, a type of printer is known where an edge guide for guiding the side of a paper is provided in the paper supply portion. As this edge guide is slid by the user to match the width of a paper when paper of a different size is set in the paper supply portion, if the sliding of this edge guide is linked to the sliding operation of the supporting portion, there is the benefit of reducing the inconvenience of having to slide the supporting portion each time. However, the conventional linking assemblies that attempt to link the sliding of the edge guide to the sliding operation of the supporting portion have the following problems. That is, there are types of paper which require support on both sides thereof by a supporting portion on each side of the paper. There are also types of paper, such as thick paper such as postcards and envelopes, which do not require support on each side thereof. For example, normal types of paper such as A4 and B5 require the support on both sides of the sheet by a pair of supporting portions. By supporting both sides of the sheet, a fairly reliable discharge operation is obtained. However, when using paper such as postcards or small envelopes with comparatively narrow widths, as shown in FIG. 40, both sides of the sheet are supported by supporting portions 691a and 691b. However, since the paper is stiff and will not necessarily bend into a concave shape, a stable abutting operation (pushing out operation) where the trailing edge Pb' of a previous paper P' is urged by the leading edge P2'a of a following paper P2' is not obtained. The result is that the stacking position of discharged paper P1' is disordered and the order in which the papers lie when discharged is upset as depicted in FIG. 40.
Accordingly, a printer that overcomes the aforementioned disadvantages and limitations, readily discharges paper and readily supports and guides the paper is desired.